Electro-therapy is the application of electrical energy to the body of a human patient to provide a therapeutic effect. The therapeutic effects produced by electro-therapy include the blockage of pain, residual pain relief possibly due to the release of endorphins or other opiate-like analogs, relief from headache pain, increase of blood flow, increases in the range of motion, cartilage regrowth or regeneration, accelerated bone growth, electronic epidural for childbirth and other beneficial effects that result from the introduction of a low frequency electric field into tissue beneath the skin. Electro-therapy as defined by this application does not include electro-osmosis, electroporation, or iontophoresis, or any other process in which electrical energy such as an electrical field or electric currents are used to promote the transdermal transportation of chemicals or fluids into or out of the body. Nor does it include electrosurgery where radiofrequency electrical energy is used to cut or cauterize tissue.
Electro-therapy typically includes a non-invasive technique to introduce the electrical energy into the patient's body. Disposable electrodes are placed on the epidermal surface of a patient and coupled to an electric generator. The generator supplies two or more oscillating or complex morphology electric currents to a patient, with respective selected electrodes separated from one another on the patient's body with a pain site located directly underneath at least one electrode with the majority of the electric field positioned in a hemisphere beneath the skin surface on which each electrode resides. The electric currents have frequencies of at least about 1 KHz and differing by as little as 1 Hz up to about 250 Hz from each other. A nonlinear action of nerve fiber membranes and/or other electrochemically-active structures or fluids causes a multiplication of the two independent frequency signals in a volume of tissue surrounding and beneath each electrode to produce a therapeutic effect in depth. The mixing yields a distribution of synthesized sum and difference frequencies among which is a therapeutic low frequency equivalent to a beat frequency of the signals.
In order to penetrate the tissue beneath the skin and provide a therapeutic effect, electrical signals applied to the body must overcome the electrical impedance of the skin. Electrical impedance is a property of the skin that limits the amount of current that can pass through the skin. The top layer of the skin, the stratum corneum, is made up of dead skin cells and contributes to the skin's high electrical impedance. Dry, intact skin can have an impedance which exceeds a hundred thousand ohms. Even carefully prepared skin, i.e., where the hair has been shaved or otherwise removed, where debridement of devitalized or contaminated tissue has been performed, and where the skin's surface has been moisturized, can still have an impedance of over one thousand ohms. A potentially large voltage would be necessary to overcome the skin impedance and drive a therapeutically useful amount of electrical current at a frequency through body tissues, but the large voltage and resulting high current density may cause a significant burn at the surface of the skin. The relatively large amount of energy required, limits the voltage level that can be applied as well as the amount of time that a portable generator device powered by batteries can be used.
It is known in the art that applying electrical energy to the skin can reduce the impedance of the skin. For example, Carim et al. discloses in their U.S. Pat. No. 6,032,060 issued on Feb. 29, 2000 directing electrical energy through a medical electrode placed on the skin of the patient in order to electrically condition the skin. The reduction in skin impedance increases the ability to monitor bioelectric signals and can reduce the amount of energy necessary for electroporation or transdermal iontophoresis.
Known devices and systems are designed for sensing electrical signals generated by the body or for delivering pharmaceuticals to the body. These devices have physical characteristics and electrical properties that make them suitable for their intended uses. Thus, while methods and systems to penetrate beneath the skin to provide a therapeutic effect are known, they are generally invasive and difficult to administer. What is needed is a non or minimally invasive method and system of stimulating a nerve for a therapeutic effect, particularly methods and systems that are compatible with a Biowave® stimulator and electrodes.